Directory UMM :Data Elmu:jurnal:A:Aquaculture:Vol182.Issue3-4.Feb2000:
Aquaculture 182 Ž2000. 329–338
www.elsevier.nlrlocateraqua-online
The influence of nocturnal vs. diurnal feeding under
winter conditions on growth and feed conversion of
European sea bass žDicentrarchus labrax, L. /
M. Azzaydi ) , F.J. Martınez,
S. Zamora, F.J. Sanchez-Vazquez,
´
´
´
J.A. Madrid
Department of Physiology and Pharmacology, Faculty of Biology, UniÕersity of Murcia, 30100 Murcia, Spain
Accepted 23 July 1999
Abstract
European sea bass display predominantly nocturnal self-feeding patterns in winter and early
spring, and this has been further examined by comparing the effect of night and day feeding on
growth and feed conversion. To this end, three feeding regimes were compared: nocturnal
automatic-feeding ŽNF., diurnal automatic-feeding ŽDF. and free access to self-feeders ŽSF..
Under NF, feed was supplied in two meals differing in size Žpre-dawn and post-dusk, 33.33:
66.67% of daily feed ration, respectively.. In DF feed was supplied in three equally-sized meals
Žmorning, afternoon and evening, 33.33: 33.33: 33.33% of daily feed ration.. The experiment was
carried out from January to April. Under SF, sea bass showed a phase inversion of daily feeding
rhythms, which changed from an initial nocturnal to diurnal by the end of the experiment. Feeding
strategies affected specific growth rate ŽSGR. and feed conversion ratio ŽFCR., the highest SGR
and the lowest FCR being obtained with SF and NF treatments ŽSGR: 0.26 " 0.01 in NF vs.
0.19 " 0.01 in DF; FCR: 2.65 " 0.08 in NF vs. 3.73 " 0.17 in DF.. The results demonstrate that
feeding sea bass by night in winter, when they show nocturnal behaviour, may improve their
growth and feed efficiency. q 2000 Elsevier Science B.V. All rights reserved.
Keywords: Feeding rhythms; Growth; Feed conversion; Self-feeding; Automatic-feeding; Sea bass
1. Introduction
Knowledge about fish feeding habits is of importance in fish farming, because
feeding regime may have consequences for both growth efficiency and feed wastage.
)
Corresponding author. Tel.: q34-968-364931; fax: q34-968-363963; e-mail: mazzaydi@fcu.um.es
0044-8486r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 0 4 4 - 8 4 8 6 Ž 9 9 . 0 0 2 7 6 - 8
330
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
Intensively farmed fish are often fed regularly throughout the day on predetermined
daily feed rations, but fish display daily cycles of feeding ŽKadri et al., 1991; Alanara,
¨¨
1992a,b; Boujard and Leatherland, 1992a,b; Eriksson and Alanara,
¨ ¨ 1992; Boujard, 1995;
Jobling et al., 1995., so this feeding practice may result in under-feeding when the fish
are hungry and in over-feeding at times of low appetite.
The matching of feed supply to natural feeding rhythms may lead to improved growth
ŽNoeske et al., 1981; Sundararaj et al., 1982; Noeske and Spieler, 1984; Noeske-Hallin
et al., 1985; Kerdchuen and Legendre, 1991; Boujard et al., 1995; Gelineau
et al., 1996;
´
Azzaydi et al., 1998, 1999., but feeding preferences may change with the seasons.
Consequently, feeding time which results in best growth does not necessarily remain
unchanged throughout the year ŽLandless, 1976; Noeske and Spieler, 1984; Boujard and
Leatherland, 1992a; Fraser et al., 1993; Smith et al., 1993..
Sea bass, which are widely cultivated in the Mediterranean region, displays flexibility
in its feeding rhythms ŽAnthouard et al., 1993; Sanchez-Vazquez
et al., 1994, 1995;
´
´
Boujard et al., 1996.. Recently, it has been reported that sea bass show phase inversion
in their feeding rhythms on a seasonal basis: fish which were diurnal in summer and
autumn, changed to nocturnal in winter, and returned to being diurnal in later spring
ŽSanchez-Vazquez
et al., 1998..
´
´
In the present paper we tested whether feeding sea bass by night in winter improves
their growth performance. To this end, we compared the growth and feed conversion of
sea bass fed by automatic systems which either mimicked the natural winter feeding
rhythm Žnocturnal feeding, NF. or in which feed was supplied as three equally
sized-meals provided during daylight hours Ždiurnal feeding, DF.. A third treatment in
which fish had free access to a self-feeder ŽSF. was used to study self-feeding patterns.
2. Materials and methods
A total of 180 European sea bass Ž Dicentrarchus labrax, L.. hatched in captivity
ŽCULMAREX, Aguilas, Murcia, Spain., were used in the experiment which was carried
out from January to April. The fish, which had an initial body weight of 59.3 " 1.2 g
Žmean " SEM., were divided into 12 groups with 15 fish in each. Each group was
placed into a 460 1 experimental tank supplied with running seawater Ž37‰ salinity..
Throughout the experiment, the fish were exposed to natural photoperiod and water
temperature, which ranged from 10.25 h ŽJanuary. to 12.50 h ŽApril., and from 14.18C
ŽJanuary. to 16.88C ŽApril. ŽFig. 2.. Photoperiod Žlight level. and water temperature
were continuously registered every 15 min by means of a portable data logger ŽLogit SL,
DCP Microdevelopments and SCC Research, UK..
The fish were fed a commercial pellet feed ŽEWOS, 2 mm pellet. containing 49%
protein, 12% fat, 6.8% moisture, 11% ash and 21.2% NFE. Each tank was provided with
an electronic self-feeder which delivered approximately 8–9 pellets Žabout 0.4 g of feed.
each time a fish activated a trigger located 3 cm below the water surface ŽSanchez´
Vazquez
et al., 1994.. Feeders were checked every other day, the feed remaining was
´
weighed and the feed reservoir refilled.
All groups of fish were initially given free access to the self-feeders for 33 days. Fish
were then weighed and the three feeding regimes were established Ž4 replicates per
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
331
treatment.. In the first treatment, sea bass had free access to self-feeders ŽSF treatment.
connected to a computer which recorded the number of trigger activations in 10 min
bins. In the second and the third treatments, sea bass were fed using automatically-triggered feeders according to fixed schedules ŽFig. 1: NF and DF.. NF fish were fed in
accordance with winter self-feeding rhythms ŽSanchez-Vazquez
et al., 1998. whereas
´
´
DF fish were fed three equally-sized meals. An electronic feeder activated automatically
by a timer was used, there being a pause between each feed delivery. In the NF and DF
treatments, the daily rations were established in accordance with tables provided by the
feed manufacturer ŽEWOS..
The fish were weighed at 31, 59 and 90 days, each time after one day of feed
deprivation. This served to delimit three periods, at the start of which the daily feed
rations for NF and DF fish were adjusted in relation to body weight and temperature and
feeding times were adjusted in relation to photoperiod ŽFig. 1..
Fig. 1. Meal schedule of fish fed automatically. DF: diurnal automatic-feeding; NF: nocturnal automatic-feeding. The vertical bars represent the meals while the height and width of each bar are proportional to the size
and duration of each meal, respectively. Black and white bars at the bottom of the graphs represent the
scotophase and photophase, respectively.
332
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
333
Table 1
Effect of feeding regime on growth performance
Feeding regime
SF Ž ns 3.
NF Ž ns 4.
DF Ž ns 4.
P
Feed delivered Žg.
Biomass increase Žg.
SGR Ž% b.w.rday.
FCR
CVi
CVf
446"13 a
190"12 ab
0.22"0.02 a
2.37"0.10 a
30.24"2.87
21.32"3.91 b
629"8 b
238"9 a
0.26"0.01 a
2.65"0.08 a
27.39"1.04
20.47"1.33 b
617"12 b
166"10 b
0.19"0.01 b
3.73"0.17 b
23.49"2.09
15.91"2.41 b
- 0.0001
- 0.01
- 0.05
- 0.001
- 0.01
Means with different letters in the same line Žin the same row for CV. are significantly different ŽANOVA,
Tukey HSD, mean"SEM..
The following parameters were calculated for each period and for the duration of the
entire experiment: Specific growth rate ŽSGR. s wŽIn Žfinal biomass. y In Žinitial
biomass..rdaysx = 100 Feed conversion ratio ŽFCR. s weight feed deliveredrbiomass
gain Initial and final Coefficient of Variation ŽCVŽi or f. . s Žstandard deviation of the
individual Ži or f.weightrmean Ži or f.weight. = 100
Treatment means were compared by one-way ANOVA ŽSTATGRAPHICS 7.0
Statistical Graphics, Cambridge, MA, 1993. after log-transformation of indices and
percentages. When statistically significant differences were detected, Tukey’s multiple
range test was used a posteriori. CVi and CVi were compared by a sign-test. In all tests,
the significance level was set at P - 0.05.
3. Results
Actograms of feeding activity of SF sea bass along with temperature and photoperiod
are shown in Fig. 2. Group A was nocturnal during the two first months of the
experiment, before changing to diurnal. Group B changed from being nocturnal to
diurnal at the end of the first month of the experiment. Group C was mainly diurnal,
although during the first month of the experiment fish fed both in the photophase and
the scotophase. The results obtained from one group of SF fish and one of DF fish were
deleted because of unsolved technical problems with the self-feeding device.
Feed, demanded by SF fish and supplied to NF and DF fish, together with biomass
increase, SGR, FCR and CV are shown in Table 1. Feed demanded by SF fish was
significantly lower than that supplied to NF and DF fish.
Biomass gain was significantly greater in the NF than in the DF treatment and the
poorest SGR and FCR were recorded for DF fish. CV was calculated to ascertain the
influence of feeding regime on the range of fish weights. In all treatments, CV decreased
during the course of the experiment.
Fig. 2. Actograms of self-feeding records of 3 groups of 15 sea bass Žgroups A, B and C.. For convenient
visualization, the data have been double plotted Ž48 h time scale., each point representing the percentage of
daily requests for feed in 10 min bins. The evolution of mean daily temperature Žsolid line. and photoperiod
length Ždotted line. through the experiment are represented on the right.
334
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
Fig. 3. Evolution of SGR and FCR during the three experimental periods in sea bass fed with the three feeding
regimes. SF: sea bass having free access to the self-feeder Ž N s 3.; NF: nocturnal automatic-feeding Ž N s 4.;
DF: diurnal automatic-feeding Ž N s 3.. Means with different letters are significantly different ŽANOVA,
Tukey HSD, P - 0.05, mean"SEM..
Changes in SGR and FCR through the three periods of the experiment are shown in
Fig. 3. In the DF treatment, the poorest FCR and SGR were obtained in the first period,
while during the second and third period, FCR decreased and SGR increased. In the
contrary, in the NF treatment, FCR and SGR were better in the first and second period
than in the third period. Under SF treatment, no such a tendency was detected across the
different experimental periods, although FCR increased in the second period, coinciding
with the time of most phase inversions.
4. Discussion
There was a phase inversion of daily feeding rhythms in the self-feeding sea bass,
in that fish which were initially nocturnal were diurnal at the end of the experiment
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
335
ŽFig. 2.. These results agree with those reported previously for self-feeding sea bass
ŽAnthouard et al., 1993; Begout-Anras,
1995; Boujard et al., 1996; Madrid et al., 1997;
´
Azzaydi et al., 1998, 1999; Sanchez-Vazquez
et al., 1998. and point to a seasonal
´
´
change in feeding behaviour involving phase inversion ŽSanchez-Vazquez
et al., 1998..
´
´
One group of fish in the SF treatment which did not show well defined dual
behaviour, something which is at odds with previous observations, where all groups of
sea bass showed a phase inversion in their daily feeding patterns ŽSanchez-Vazquez
et
´
´
al., 1998.. However, not all groups of fish can be expected to display simultaneous
changes in feeding behaviour.
The lowest biomass increase, SGR and poorest FCR were observed among fish in the
DF treatment. Nevertheless, the evolution of growth performance during the experiment
deserves detailed comment. Our results of FCR in treatment DF are in agreement with
those described by Barnabe´ Ž1986. under winter environmental conditions. However, the
SGR and FCR seemed worse than those previously reported for sea bass of similar size
and under high temperature ŽDivanach et al., 1993; Boujard et al., 1996; Azzaydi et al.,
1998a. or, of larger size and under the same temperature ŽAnthouard et al., 1993..
Although comparisons between experiments must be made with caution, these discrepancies may be due to the following reasons: Ža. the temperature conditions used in this
trial, which were far from the ‘‘optimum’’ estimated for feeding sea bass ŽBarnabe,
´
1986.; Žb. the feed losses due to reward level for each trigger activation, used in our
experiment Ž8–9 pellets for 15 fish., which probably exceeded the consumption capacity
of sea bass due to low feeding motivation. For instance, Alanara
¨ ¨ Ž1996. reported a
strong relationship between the level of reward and temperature conditions in rainbow
trout.
Fish of the SF group grew better than those of the DF group, which is in agreement
with previous findings for sea bream ŽDivanach et al., 1986; Kentouri et al., 1993.,
rainbow trout ŽAlanara,
¨ ¨ 1992a. and sea bass ŽAzzaydi et al., 1998, 1999.: feeding fish in
phase with their natural feeding rhythms may improve growth performance Žsee reviews
Boujard and Leatherland, 1992a; Jobling et al., 1995; Thorpe and Cho, 1995., a view
corroborated by our results, in which SF and NF fish showed similar growth and feed
conversion.
Although growth was better in sea bass fed by night ŽNF treatment. than by day
ŽDF., the poor overall FCR and SGR ŽTable 1. observed for fish in the DF treatment
were mainly due a poor performance during the first period of the experiment ŽFig. 3..
Perhaps this period might be regarded as a learning or adaptation period, because
feeding times were shifted from those regarded as natural, whereas fish in the NF
treatment were exposed to predetermined meal cycle matched to the natural feeding
rhythm. The poorest growth of NF fish Žthird period. and DF fish Žfirst period.
coincided with the diurnalism and nocturnalism of SF fish, respectively. These findings
are in broad agreement with those of Boujard Ž1995. who observed a reduction in the
voluntary feed intake of catfish Ž Silurus glanis ., a nocturnal species, trained to self-feed
in the photophase. The FCR and SGR of treatment groups in the second experimental
period were similar to which were obtained in the first period in NF and in the third
period in DF treatment, suggesting that an automatic feeding schedule may exert some
synchronising effects on feeding activity inducing a delay, in NF, and an advance, in
336
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
DF, in the time of feeding inversions from diurnal to nocturnal. The ability of restricted
feeding schedules to induce phase inversions in feeding rhythms in sea bass was
previously reported ŽSanchez-Vazquez
et al., 1995..
´
´
The CVSf were significantly smaller than CVSi Ž P - 0.01. in all treatments, indicating that all groups became more homogeneous with the passage of time. This is in
accordance with previous findings for groups of sea bass submitted to different feeding
strategies and fed using the same level of reward for each trigger activation Ž8–9 pellets
for 15 fish. ŽAzzaydi et al., 1998, 1999..
Sea bass shift their daily feeding patterns from nocturnal to diurnal in winter and
early spring, and feeding sea bass by night, in winter, may result in improved growth
performance. Although the flexibility of sea bass feeding habits enabled fish to adapt to
diurnal feeding, one cost of adaptation to feeding out of phase with the natural feeding
rhythms seem to be reduced growth. Further work is needed to assess any benefits there
might be in nocturnal feeding of sea bass under farming conditions.
5. Further reading
Anthouard et al., 1986; Hidalgo et al., 1988
Acknowledgements
This research was supported by grants from the ‘‘Comision
´ Interministerial de
Ciencia y Tecnologıa’’
´ ŽCICYT, no. AGF95-0459 to J.A. Madrid. and from the
‘‘Comunidad Autonoma de la Region
´ de Murcia’’ ŽCARM, FI-con 96r9 to J.A.
Madrid.. The authors wish to acknowledge Dr. Benjamın
´ Garcıa
´ and other staff from the
‘‘Centro de Recursos Marinos y Humedales del Litoral de San Pedro del Pinatar’’ for
their kind support and assistance during the experiments. We are also grateful to
Culmarex for supplying the sea bass and the ‘‘Agencia Espanola
de Cooperacion
˜
´
Internacional ŽICMAMPD.’’, for the financial aid received by M. Azzaydi.
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www.elsevier.nlrlocateraqua-online
The influence of nocturnal vs. diurnal feeding under
winter conditions on growth and feed conversion of
European sea bass žDicentrarchus labrax, L. /
M. Azzaydi ) , F.J. Martınez,
S. Zamora, F.J. Sanchez-Vazquez,
´
´
´
J.A. Madrid
Department of Physiology and Pharmacology, Faculty of Biology, UniÕersity of Murcia, 30100 Murcia, Spain
Accepted 23 July 1999
Abstract
European sea bass display predominantly nocturnal self-feeding patterns in winter and early
spring, and this has been further examined by comparing the effect of night and day feeding on
growth and feed conversion. To this end, three feeding regimes were compared: nocturnal
automatic-feeding ŽNF., diurnal automatic-feeding ŽDF. and free access to self-feeders ŽSF..
Under NF, feed was supplied in two meals differing in size Žpre-dawn and post-dusk, 33.33:
66.67% of daily feed ration, respectively.. In DF feed was supplied in three equally-sized meals
Žmorning, afternoon and evening, 33.33: 33.33: 33.33% of daily feed ration.. The experiment was
carried out from January to April. Under SF, sea bass showed a phase inversion of daily feeding
rhythms, which changed from an initial nocturnal to diurnal by the end of the experiment. Feeding
strategies affected specific growth rate ŽSGR. and feed conversion ratio ŽFCR., the highest SGR
and the lowest FCR being obtained with SF and NF treatments ŽSGR: 0.26 " 0.01 in NF vs.
0.19 " 0.01 in DF; FCR: 2.65 " 0.08 in NF vs. 3.73 " 0.17 in DF.. The results demonstrate that
feeding sea bass by night in winter, when they show nocturnal behaviour, may improve their
growth and feed efficiency. q 2000 Elsevier Science B.V. All rights reserved.
Keywords: Feeding rhythms; Growth; Feed conversion; Self-feeding; Automatic-feeding; Sea bass
1. Introduction
Knowledge about fish feeding habits is of importance in fish farming, because
feeding regime may have consequences for both growth efficiency and feed wastage.
)
Corresponding author. Tel.: q34-968-364931; fax: q34-968-363963; e-mail: mazzaydi@fcu.um.es
0044-8486r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 0 4 4 - 8 4 8 6 Ž 9 9 . 0 0 2 7 6 - 8
330
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
Intensively farmed fish are often fed regularly throughout the day on predetermined
daily feed rations, but fish display daily cycles of feeding ŽKadri et al., 1991; Alanara,
¨¨
1992a,b; Boujard and Leatherland, 1992a,b; Eriksson and Alanara,
¨ ¨ 1992; Boujard, 1995;
Jobling et al., 1995., so this feeding practice may result in under-feeding when the fish
are hungry and in over-feeding at times of low appetite.
The matching of feed supply to natural feeding rhythms may lead to improved growth
ŽNoeske et al., 1981; Sundararaj et al., 1982; Noeske and Spieler, 1984; Noeske-Hallin
et al., 1985; Kerdchuen and Legendre, 1991; Boujard et al., 1995; Gelineau
et al., 1996;
´
Azzaydi et al., 1998, 1999., but feeding preferences may change with the seasons.
Consequently, feeding time which results in best growth does not necessarily remain
unchanged throughout the year ŽLandless, 1976; Noeske and Spieler, 1984; Boujard and
Leatherland, 1992a; Fraser et al., 1993; Smith et al., 1993..
Sea bass, which are widely cultivated in the Mediterranean region, displays flexibility
in its feeding rhythms ŽAnthouard et al., 1993; Sanchez-Vazquez
et al., 1994, 1995;
´
´
Boujard et al., 1996.. Recently, it has been reported that sea bass show phase inversion
in their feeding rhythms on a seasonal basis: fish which were diurnal in summer and
autumn, changed to nocturnal in winter, and returned to being diurnal in later spring
ŽSanchez-Vazquez
et al., 1998..
´
´
In the present paper we tested whether feeding sea bass by night in winter improves
their growth performance. To this end, we compared the growth and feed conversion of
sea bass fed by automatic systems which either mimicked the natural winter feeding
rhythm Žnocturnal feeding, NF. or in which feed was supplied as three equally
sized-meals provided during daylight hours Ždiurnal feeding, DF.. A third treatment in
which fish had free access to a self-feeder ŽSF. was used to study self-feeding patterns.
2. Materials and methods
A total of 180 European sea bass Ž Dicentrarchus labrax, L.. hatched in captivity
ŽCULMAREX, Aguilas, Murcia, Spain., were used in the experiment which was carried
out from January to April. The fish, which had an initial body weight of 59.3 " 1.2 g
Žmean " SEM., were divided into 12 groups with 15 fish in each. Each group was
placed into a 460 1 experimental tank supplied with running seawater Ž37‰ salinity..
Throughout the experiment, the fish were exposed to natural photoperiod and water
temperature, which ranged from 10.25 h ŽJanuary. to 12.50 h ŽApril., and from 14.18C
ŽJanuary. to 16.88C ŽApril. ŽFig. 2.. Photoperiod Žlight level. and water temperature
were continuously registered every 15 min by means of a portable data logger ŽLogit SL,
DCP Microdevelopments and SCC Research, UK..
The fish were fed a commercial pellet feed ŽEWOS, 2 mm pellet. containing 49%
protein, 12% fat, 6.8% moisture, 11% ash and 21.2% NFE. Each tank was provided with
an electronic self-feeder which delivered approximately 8–9 pellets Žabout 0.4 g of feed.
each time a fish activated a trigger located 3 cm below the water surface ŽSanchez´
Vazquez
et al., 1994.. Feeders were checked every other day, the feed remaining was
´
weighed and the feed reservoir refilled.
All groups of fish were initially given free access to the self-feeders for 33 days. Fish
were then weighed and the three feeding regimes were established Ž4 replicates per
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
331
treatment.. In the first treatment, sea bass had free access to self-feeders ŽSF treatment.
connected to a computer which recorded the number of trigger activations in 10 min
bins. In the second and the third treatments, sea bass were fed using automatically-triggered feeders according to fixed schedules ŽFig. 1: NF and DF.. NF fish were fed in
accordance with winter self-feeding rhythms ŽSanchez-Vazquez
et al., 1998. whereas
´
´
DF fish were fed three equally-sized meals. An electronic feeder activated automatically
by a timer was used, there being a pause between each feed delivery. In the NF and DF
treatments, the daily rations were established in accordance with tables provided by the
feed manufacturer ŽEWOS..
The fish were weighed at 31, 59 and 90 days, each time after one day of feed
deprivation. This served to delimit three periods, at the start of which the daily feed
rations for NF and DF fish were adjusted in relation to body weight and temperature and
feeding times were adjusted in relation to photoperiod ŽFig. 1..
Fig. 1. Meal schedule of fish fed automatically. DF: diurnal automatic-feeding; NF: nocturnal automatic-feeding. The vertical bars represent the meals while the height and width of each bar are proportional to the size
and duration of each meal, respectively. Black and white bars at the bottom of the graphs represent the
scotophase and photophase, respectively.
332
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
333
Table 1
Effect of feeding regime on growth performance
Feeding regime
SF Ž ns 3.
NF Ž ns 4.
DF Ž ns 4.
P
Feed delivered Žg.
Biomass increase Žg.
SGR Ž% b.w.rday.
FCR
CVi
CVf
446"13 a
190"12 ab
0.22"0.02 a
2.37"0.10 a
30.24"2.87
21.32"3.91 b
629"8 b
238"9 a
0.26"0.01 a
2.65"0.08 a
27.39"1.04
20.47"1.33 b
617"12 b
166"10 b
0.19"0.01 b
3.73"0.17 b
23.49"2.09
15.91"2.41 b
- 0.0001
- 0.01
- 0.05
- 0.001
- 0.01
Means with different letters in the same line Žin the same row for CV. are significantly different ŽANOVA,
Tukey HSD, mean"SEM..
The following parameters were calculated for each period and for the duration of the
entire experiment: Specific growth rate ŽSGR. s wŽIn Žfinal biomass. y In Žinitial
biomass..rdaysx = 100 Feed conversion ratio ŽFCR. s weight feed deliveredrbiomass
gain Initial and final Coefficient of Variation ŽCVŽi or f. . s Žstandard deviation of the
individual Ži or f.weightrmean Ži or f.weight. = 100
Treatment means were compared by one-way ANOVA ŽSTATGRAPHICS 7.0
Statistical Graphics, Cambridge, MA, 1993. after log-transformation of indices and
percentages. When statistically significant differences were detected, Tukey’s multiple
range test was used a posteriori. CVi and CVi were compared by a sign-test. In all tests,
the significance level was set at P - 0.05.
3. Results
Actograms of feeding activity of SF sea bass along with temperature and photoperiod
are shown in Fig. 2. Group A was nocturnal during the two first months of the
experiment, before changing to diurnal. Group B changed from being nocturnal to
diurnal at the end of the first month of the experiment. Group C was mainly diurnal,
although during the first month of the experiment fish fed both in the photophase and
the scotophase. The results obtained from one group of SF fish and one of DF fish were
deleted because of unsolved technical problems with the self-feeding device.
Feed, demanded by SF fish and supplied to NF and DF fish, together with biomass
increase, SGR, FCR and CV are shown in Table 1. Feed demanded by SF fish was
significantly lower than that supplied to NF and DF fish.
Biomass gain was significantly greater in the NF than in the DF treatment and the
poorest SGR and FCR were recorded for DF fish. CV was calculated to ascertain the
influence of feeding regime on the range of fish weights. In all treatments, CV decreased
during the course of the experiment.
Fig. 2. Actograms of self-feeding records of 3 groups of 15 sea bass Žgroups A, B and C.. For convenient
visualization, the data have been double plotted Ž48 h time scale., each point representing the percentage of
daily requests for feed in 10 min bins. The evolution of mean daily temperature Žsolid line. and photoperiod
length Ždotted line. through the experiment are represented on the right.
334
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
Fig. 3. Evolution of SGR and FCR during the three experimental periods in sea bass fed with the three feeding
regimes. SF: sea bass having free access to the self-feeder Ž N s 3.; NF: nocturnal automatic-feeding Ž N s 4.;
DF: diurnal automatic-feeding Ž N s 3.. Means with different letters are significantly different ŽANOVA,
Tukey HSD, P - 0.05, mean"SEM..
Changes in SGR and FCR through the three periods of the experiment are shown in
Fig. 3. In the DF treatment, the poorest FCR and SGR were obtained in the first period,
while during the second and third period, FCR decreased and SGR increased. In the
contrary, in the NF treatment, FCR and SGR were better in the first and second period
than in the third period. Under SF treatment, no such a tendency was detected across the
different experimental periods, although FCR increased in the second period, coinciding
with the time of most phase inversions.
4. Discussion
There was a phase inversion of daily feeding rhythms in the self-feeding sea bass,
in that fish which were initially nocturnal were diurnal at the end of the experiment
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
335
ŽFig. 2.. These results agree with those reported previously for self-feeding sea bass
ŽAnthouard et al., 1993; Begout-Anras,
1995; Boujard et al., 1996; Madrid et al., 1997;
´
Azzaydi et al., 1998, 1999; Sanchez-Vazquez
et al., 1998. and point to a seasonal
´
´
change in feeding behaviour involving phase inversion ŽSanchez-Vazquez
et al., 1998..
´
´
One group of fish in the SF treatment which did not show well defined dual
behaviour, something which is at odds with previous observations, where all groups of
sea bass showed a phase inversion in their daily feeding patterns ŽSanchez-Vazquez
et
´
´
al., 1998.. However, not all groups of fish can be expected to display simultaneous
changes in feeding behaviour.
The lowest biomass increase, SGR and poorest FCR were observed among fish in the
DF treatment. Nevertheless, the evolution of growth performance during the experiment
deserves detailed comment. Our results of FCR in treatment DF are in agreement with
those described by Barnabe´ Ž1986. under winter environmental conditions. However, the
SGR and FCR seemed worse than those previously reported for sea bass of similar size
and under high temperature ŽDivanach et al., 1993; Boujard et al., 1996; Azzaydi et al.,
1998a. or, of larger size and under the same temperature ŽAnthouard et al., 1993..
Although comparisons between experiments must be made with caution, these discrepancies may be due to the following reasons: Ža. the temperature conditions used in this
trial, which were far from the ‘‘optimum’’ estimated for feeding sea bass ŽBarnabe,
´
1986.; Žb. the feed losses due to reward level for each trigger activation, used in our
experiment Ž8–9 pellets for 15 fish., which probably exceeded the consumption capacity
of sea bass due to low feeding motivation. For instance, Alanara
¨ ¨ Ž1996. reported a
strong relationship between the level of reward and temperature conditions in rainbow
trout.
Fish of the SF group grew better than those of the DF group, which is in agreement
with previous findings for sea bream ŽDivanach et al., 1986; Kentouri et al., 1993.,
rainbow trout ŽAlanara,
¨ ¨ 1992a. and sea bass ŽAzzaydi et al., 1998, 1999.: feeding fish in
phase with their natural feeding rhythms may improve growth performance Žsee reviews
Boujard and Leatherland, 1992a; Jobling et al., 1995; Thorpe and Cho, 1995., a view
corroborated by our results, in which SF and NF fish showed similar growth and feed
conversion.
Although growth was better in sea bass fed by night ŽNF treatment. than by day
ŽDF., the poor overall FCR and SGR ŽTable 1. observed for fish in the DF treatment
were mainly due a poor performance during the first period of the experiment ŽFig. 3..
Perhaps this period might be regarded as a learning or adaptation period, because
feeding times were shifted from those regarded as natural, whereas fish in the NF
treatment were exposed to predetermined meal cycle matched to the natural feeding
rhythm. The poorest growth of NF fish Žthird period. and DF fish Žfirst period.
coincided with the diurnalism and nocturnalism of SF fish, respectively. These findings
are in broad agreement with those of Boujard Ž1995. who observed a reduction in the
voluntary feed intake of catfish Ž Silurus glanis ., a nocturnal species, trained to self-feed
in the photophase. The FCR and SGR of treatment groups in the second experimental
period were similar to which were obtained in the first period in NF and in the third
period in DF treatment, suggesting that an automatic feeding schedule may exert some
synchronising effects on feeding activity inducing a delay, in NF, and an advance, in
336
M. Azzaydi et al.r Aquaculture 182 (2000) 329–338
DF, in the time of feeding inversions from diurnal to nocturnal. The ability of restricted
feeding schedules to induce phase inversions in feeding rhythms in sea bass was
previously reported ŽSanchez-Vazquez
et al., 1995..
´
´
The CVSf were significantly smaller than CVSi Ž P - 0.01. in all treatments, indicating that all groups became more homogeneous with the passage of time. This is in
accordance with previous findings for groups of sea bass submitted to different feeding
strategies and fed using the same level of reward for each trigger activation Ž8–9 pellets
for 15 fish. ŽAzzaydi et al., 1998, 1999..
Sea bass shift their daily feeding patterns from nocturnal to diurnal in winter and
early spring, and feeding sea bass by night, in winter, may result in improved growth
performance. Although the flexibility of sea bass feeding habits enabled fish to adapt to
diurnal feeding, one cost of adaptation to feeding out of phase with the natural feeding
rhythms seem to be reduced growth. Further work is needed to assess any benefits there
might be in nocturnal feeding of sea bass under farming conditions.
5. Further reading
Anthouard et al., 1986; Hidalgo et al., 1988
Acknowledgements
This research was supported by grants from the ‘‘Comision
´ Interministerial de
Ciencia y Tecnologıa’’
´ ŽCICYT, no. AGF95-0459 to J.A. Madrid. and from the
‘‘Comunidad Autonoma de la Region
´ de Murcia’’ ŽCARM, FI-con 96r9 to J.A.
Madrid.. The authors wish to acknowledge Dr. Benjamın
´ Garcıa
´ and other staff from the
‘‘Centro de Recursos Marinos y Humedales del Litoral de San Pedro del Pinatar’’ for
their kind support and assistance during the experiments. We are also grateful to
Culmarex for supplying the sea bass and the ‘‘Agencia Espanola
de Cooperacion
˜
´
Internacional ŽICMAMPD.’’, for the financial aid received by M. Azzaydi.
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